In many cases, MRI apparatuses have been utilized to inspect cephalic regions, for example. It has been also expected that PET apparatuses are utilized to inspect cephalic regions, e.g., to diagnose Alzheimer diseases. Hence, recently, it has been expected to realize a PET-MRI apparatus combining a PET apparatus and an MRI apparatus.
The MRI apparatuses, however, have some limitations. For example, a photomultiplier tube (PMT) used as a detector of a conventional PET apparatus cannot be used when the PET-MRI apparatus is intended to be realized because a strong radio frequency magnetic field is used in the MRI apparatus. Therefore, a PET-MRI apparatus has been proposed that uses an APD (Avalanche Photodiode) or a SiPM (Silicon Photomultiplier) instead of the PMT, for example.
In some conventional PET-MRI apparatuses, an SNR (Signal-to-Noise Ratio) of an MR image is lowered due to the interference between a detector and signal lines that are elements of the PET apparatus and a transmitting radio frequency coil that is an element of the MRI apparatus.